Recently, low-energy pulse neutron has been watched as the radiation-source for an advanced neutron medical treatment such as BNCT (boron neutron capture therapy). It has been known that the neutron for BNCT, epithermal neutron being generally in the region of 1 eV˜10 keV and thermal neutron being generally 0.5 eV or less, are effective.
For the above neutron, continuous wave (non-pulse) neutron produced with a nuclear reactor has been conventionally used. However, the nuclear reactor cannot be installed in hospitals due to its huge size. On that account, an attempt to use pulse neutron which can be produced with an accelerator has been recently watched.
Methods and apparatuses which are able to measure and monitor accurate energy-spectra, doses, irradiation positions and transmission image of pulse neutron for BNCT have been demanded.
For example, the method and apparatus to measure energy spectra of pulse neutron with TOF (time-of-flight) have been presented (Non-Patent Document 1).
Non-Patent Document 1 have disclosed the CASCADE neutron-detector equipping GEM (gas-electron multiplier) coated with 10B and CIPix-ASIC and FPGA as the microprocessor. The documents have disclosed the relationship between the wavelength of neutron vs detection-efficiency of GEM which was measured by TOF using a neutron-source of the neutron beam line CT2-PF1-A. The documents have reported that an energy spectrum of neutron being in the range of 1.8 Å˜25 Å in wavelength was measured at a TOF-range of 1 ms˜23 ms. The wavelength of 1.8 Å˜25 Å can be converted into kinetic energy and velocity, 1.8 Å: 2.53×10−2 eV, 2,200 m/sec ; 25 Å: 1.3×10−4 eV, 11.4 m/sec; respectively, which is corresponding to those for so-called cold neutron. Neutron produced with the above CT2-PF1-A (the neutron beam line at J-PARC) was Neutron produced by radiating accelerated proton beam upon a target material. Neutron has contained cold neutron, thermal neutron and epithermal neutron and the like. However, neutron which has been measured with the CASCADE neutron-detector described in the document was only cold neutron in a TOF-range of 1 ms˜23 ms. Therefore, it is recognized that the CASCADE neutron-detector disclosed in the document could measure only cold neutron.
As described above, a neutron detector which is able to measure and monitor precise energy spectra, doses, irradiation positions and transmission image of pulse neutron for BNCT have been demanded. However, the detector as achieving such demand has been scarcely known.